Of various types of networks in which information terminals are connected to one another, wireless communications have advantages over wired communications. Examples of the advantages include excellent terminal portability and placement flexibility, and a lightweight body achievable due to elimination of cable wires. Thus, the wireless communications apparatuses are now used not only for conventional usage, that is, data transmission used with personal computers, but also for transmitting video or audio by being incorporated in many kinds of home electrical appliances.
While the wireless communications apparatuses have such advantages, there is also a drawback that transmission characteristics may be degraded because communications is performed by emitting electromagnetic waves into space. More specifically, the space where many reflectors are present is affected by fading caused due to arrival radio waves (delay waves) reflected from an object. In the environment where a transmitting apparatus and a receiving apparatus are remotely present, insufficient strength of received signals can cause reception errors.
As a measure for reducing these negative influences, there is a method for stabilizing transmission by controlling the directivity of a transmitting and receiving antenna according to the radio propagation environment. One example of such technique is a smart antenna technique disclosed in Patent Literature 1 (hereinafter, referred to as PTL 1).
The smart antenna disclosed in PTL 1 changes weights for input and output signals of antenna elements, to change the directivity of the antenna through signal processing operations. In the smart antenna disclosed in PTL 1, the optimal configuration is determined by scanning all antenna configurations.